Effect of support on printed properties in fused deposition modelling processes

ABSTRACT

Additive manufacturing still suffers from redundant support material usage when printing parts with overhanging features. All the supports will be removed after fabrication, resulting in wasted materials. There are many works conducted for reducing support waste by improving support strategies. However, using different support strategies may lead to different printed qualities. In this paper, the effect of support strategy on printed qualities is investigated in fused deposition modelling processes. Three different support strategies are adopted for manufacturing the same 3D part. The finished surface roughness and flexural properties are compared for evaluating different support strategies, as well as the material waste and printing time. The results show that different support strategies may result in different printed surface roughness and flexural properties. To achieve the balance between support consumption and properties of printed parts, it becomes necessary to understand the effect of supports on printed qualities for choosing a best support strategy.     

基于多喷头并联的3D打印机控制系统的研究

针对现有的单喷头3D打印机在打印大体积模型或零件时打印时间长、打印精度低等问题,提出了一种基于多喷头并联的3D打印机控制系统的设计方法,实现在模型切片平面的多轨迹并联打印。设计了光固化树脂并联打印喷头;采用主从式系统结构,以双STM32F407ZGT为核心、双PCL6045BL和CPLD（complex programable logic device,复杂可编程逻辑器件）为控制终端,搭建了一套双CPU （central processing unit,中央处理单元）的嵌入式3D打印机硬件控制系统;基于喷头切向跟踪原理和等间距打印原则,推导了二轴-四轴插补数据转换算法,实现了“二轴”轨迹数据到“四轴”插补加工数据的转换;设计了并联打印数据预处理程序、并联打印控制程序和并联打印脉冲输出控制程序以实现多轨迹并联打印控制;进行了控制系统的实验测试,对比了多喷头并联与单喷头3D打印机的实际打印效果。结果表明：与传统的单喷头打印方式相比,采用多喷头并联打印方式可以显著提高打印效率和打印精度,且打印质量较好。研究结果为大体积打印件的快速加工成型提供了一种切实可行的解决方案,具有一定的实用价值。     

液压式熏香3D打印机参数试验与结果分析

目的 研究了熏香3D打印机的初级试验参数,达到为后续优化和批量生产提供技术规范和数据支持的目的。方法 基于课题组前期设计试制的熏香3D打印机进行试验,通过试验分析挤出压力、打印速度、出料口与打印平台的距离、模型复杂程度、出料口直径、水料混合比等参数对熏香3D打印机的打印效果和打印效率的影响,分析研究影响熏香打印机的主、次参数。结果 挤出压力为0.4～0.6 MPa,打印速度为1800～2400 mm/min时,打印效果较好;出料口与打印平台的最适宜距离为10～12 mm。结论 挤出压力与打印速度是影响熏香成型效果的最重要的2个因素。     

Modelling and characterisation for the responsive performance of CF/PLA and CF/PEEK smart materials fabricated by 4D printing

4D printing, which is the combination of 3D printing technology and printable smart materials, provides the potential of automating actuation devices. In this paper, we have used a modified-fused deposition modelling 3D printing technology to fabricate a double-layer laminate smart material, which can be activated by temperature directly or by an electric circuit indirectly. A double-layer laminate mathematical model has been developed to describe the bending behaviour caused by the mismatch strain between the surface layer and the basal layer. The electrocaloric deformation testings were performed to find the different bending rules of this low-cost printed active composite in different physical states. The considerable maximal deformation values and deformation force (7?mm and 100?mN for these carbon fibre (CF)/polylactic acid specimens, and 10?mm and 200?mN for these CF/polyether-ether-ketone specimens in the paper) provide this double-layer smart material and 4D printing method the prospective to be applied in biomimetic sensors, actuators, transducers, and artificial muscles.     

Flexural properties of three-dimensional printed continuous wire polymer composites

Recently, continuous fibre reinforcement has been combined with three-dimensional (3D) printing to create stiffer printed components. This study investigates the effect of wire volume fraction, type of polymer matrix, and wire treatment on the flexural properties of 3D printed continuous wire polymer composites (CWPCs) through a design of experiment study. CWPC samples were printed using a modified, open-source 3D printer. The flexural properties were measured and compared to non-reinforced samples. An analytical model was developed to describe the stress distribution across unidirectional CWPCs as a function of the geometrical printing parameters, reinforcement dimensions, and material properties. Sample failure analysis was performed to investigate failure modes and offer insight into further enhancement of the composite’s properties.     

Investigation on the effect of surface modification of 3D printed parts by nanoclay and dimethyl ketone

Fused deposition modeling (FDM) has emerged as one of the most utilized 3D printing technique. However, the surface properties of the FDM built parts lacks integrity due to layer by layer manufacturing technique. Therefore, post treatment is done on FDM printed parts. In the present research work, an effort has been made to improve the surface properties of the 3D printed parts by surface modification via chemical/nanoparticles. Nanoclay and dimethyl ketone were utilized for the surface modification of acrylonitrile butadiene styrene specimens. Parameters namely nanoclay content, immersion time, heat treatment and layer thickness were investigated to study their effect on surface roughness, surface hardness and dimensions. Also, the effect of nanoclay on UV absorbance of 3D printed parts was observed. Structural and morphological analysis was performed to characterize the surface of the 3D printed specimens after surface modification process. The results show that the surface roughness was reduced by 94.9%, surface hardness was increased by 9.7% while maintaining minimum dimensional deviation of ?0.03 and +0.07?mm. Also, UV absorbance was increased in 350–380?nm range. The results of the present study highlight the capability of the surface modification process for improving the surface properties of FDM parts.     

水性和UV喷墨印刷油墨对文字线条印刷质量的影响

目的 研究Epson水性油墨与UV油墨对线条印刷质量的影响。方法 采用Epson水性油墨打印机和UV喷墨打印机在相同分辨率设置和相同纸张表面分别打印2种油墨的测试标版, 运用PIAS?-II图像分析系统, 对各个打印样张垂直方向阳线进行测量, 保存测量数据。结果 由Epson水性油墨打印获得的印刷线条宽度均匀、 光滑清晰, 而UV油墨打印获得的印刷线条宽度波动较大、 粗糙模糊。结论 对于精细的文字线条印刷品来讲, Epson水性油墨具有良好的表现能力, 可以满足较高的质量要求。     

Printability and fire performance of a developed 3D printable fibre reinforced cementitious composites under elevated temperatures

ABSTRACT

To demonstrate printability and fire performance of 3D printable fibre reinforced cementitious materials at elevated temperatures, large-scaling printing and fire performance testing are required for engineering applications. In this work, a mixture design of 3D printable fibre reinforced cementitious composite (3DPFRCC) for large-scale printing was developed. A structure with dimensions of 78 × 60 × 90?cm (L × W × H) was printed by a gantry printer in 150?min, which demonstrates that the developed 3DPFRCC mixture possesses good buildability. The rheological property, setting-time, and mechanical properties under normal and elevated temperatures of the developed 3DPFRCC were then characterised. Final results indicate that the developed 3DPFRCC is suitable for engineering applications due to its good printability and mechanical properties under normal and elevated temperatures.     

3D Printing of Diamond Tools for Dental Ceramics Processing

This paper is focused on preparing diamond tools with orderly arranged abrasive particles for dental ceramics processing via 3D printing. This allows one to overcome such drawbacks of the existing methods of dental ceramics processing as weak bonding strength, short service life, and irregular diamond distribution in diamond tools. Firstly, the CAD model of the dental diamond tool is constructed using 3D cartographic software, with level‐scan‐path geometry information generated via hierarchcal slicing. Then, using Ni–Cr alloy powder and diamond as raw materials, the dental ceramics processing diamond tool with orderly arranged diamond particles is prepared via a 3D printer. Next, an X‐ray diffractometer, energy dispersive spectrometer, and scanning electron microscope are used to analyze the microstructure of the Ni–Cr alloy and diamond particle interfaces, resulting in the identification of their bonding mechanism. Finally, the diamond grinding wheel produced by 3D printing is subjected to dental zirconia ceramics grinding performance tests. The results obtained confirm that diamond particles experience normal wear, while no abrasive falling off occurs on the 3D printed diamond tool surface.

     

High‐Performance Materials for 3D Printing in Chemical Synthesis Applications

3D printing has emerged as an enabling technology for miniaturization. High‐precision printing techniques such as stereolithography are capable of printing microreactors and lab‐on‐a‐chip devices for efficient parallelization of biological and biochemical reactions under reduced uptake of reactants. In the world of chemistry, however, up until now, miniaturization has played a minor role. The chemical and thermal stability of regular 3D printing resins is insufficient for sustaining the harsh conditions of chemical reactions. Novel material formulations that produce highly stable 3D‐printed chips are highly sought for bringing chemistry up‐to‐date on the development of miniaturization. In this work, a brief review of recent developments in highly stable materials for 3D printing is given. This work focuses on three highly stable 3D‐printable material systems: transparent silicate glasses, ceramics, and fluorinated polymers. It is further demonstrated that 3D printing is also a versatile technique for surface structuring of polymers to enhance their wetting performance. Such micro/nanostructuring is key to selectively wetting surface patterns that are versatile for chemical arrays and droplet synthesis.     

Lignin‐Based Direct Ink Printed Structural Scaffolds

3D printing of lignocellulosic biomass (cellulose, hemicellulose, and lignin) has attracted increasing attention by using this abundant, sustainable, and ecofriendly material. While cellulose can be easily tailored into a highly viscous ink for 3D printing, after solvent evaporation, the final printed structures become highly porous, fragile, and easily fall apart in water due to its hydrophilic nature. Lignin, another crucial component of natural lignocellulose, has not yet been reported for ink printing due to its unfavorable rheological behavior. Herein, a low‐cost direct ink printing strategy is developed to fabricate lignin‐based 3D structures with lignin no further refined and a more compact microstructure as well as different functionalities compared with printed cellulose. By using a soft triblock copolymer as the crosslinking agent, the rheology of lignin‐based inks can be adjusted from soft to rigid, and even enables vertical printing which requires stiff and self‐supporting features. The lignin‐based inks contain less water (≈40 wt%) and exhibit a much denser, stiffer structure, resulting in a wet tensile strength of ≈30 MPa, compared to only ≈0.6 MPa for printed cellulose. In addition, the unique macromolecular structure of lignin also demonstrates significantly improved stability in water and under heat, as well as UV‐blocking performance.     

3D Printed Polymer Photodetectors

Extrusion‐based 3D printing, an emerging technology, has been previously used in the comprehensive fabrication of light‐emitting diodes using various functional inks, without cleanrooms or conventional microfabrication techniques. Here, polymer‐based photodetectors exhibiting high performance are fully 3D printed and thoroughly characterized. A semiconducting polymer ink is printed and optimized for the active layer of the photodetector, achieving an external quantum efficiency of 25.3%, which is comparable to that of microfabricated counterparts and yet created solely via a one‐pot custom built 3D‐printing tool housed under ambient conditions. The devices are integrated into image sensing arrays with high sensitivity and wide field of view, by 3D printing interconnected photodetectors directly on flexible substrates and hemispherical surfaces. This approach is further extended to create integrated multifunctional devices consisting of optically coupled photodetectors and light‐emitting diodes, demonstrating for the first time the multifunctional integration of multiple semiconducting device types which are fully 3D printed on a single platform. The 3D‐printed optoelectronic devices are made without conventional microfabrication facilities, allowing for flexibility in the design and manufacturing of next‐generation wearable and 3D‐structured optoelectronics, and validating the potential of 3D printing to achieve high‐performance integrated active electronic materials and devices.     

石膏的直写成型：可打印石膏浆料的研制

石膏是雕像、建筑和铸造模具(合金和陶瓷)的常用材料。采用直写成型(Direct Ink Writing, DIW)打印石膏可避免其他3D打印技术(如Binder Jetting, PBBJ等)中存在水化反应不充分等问题, 获得高强度3D打印石膏。为了延缓水化反应获得充足的打印操作时间, 本研究通过添加缓凝剂和增稠剂, 研制了一种适用于直写成型的石膏浆料, 并打印了多种石膏三维结构(如蜘蛛网和木材堆积结构等)。结果表明, 质量分数为0.6%柠檬酸(Citric Acid, CA)的缓凝效果最好, 极大地减少了石膏流动性的经时损失。质量分数为0.3%羟丙基甲基纤维素(Hydroxypropyl Methylcellulose, HPMC)的增稠效果最好, 使石膏浆料具有良好的打印性能。CA的选择性吸附使得石膏晶体定向生长, 延长水化反应时间, 但一定程度降低石膏强度。HPMC加速石膏浆料中絮凝结构形成, 导致其粘度和剪切弹性模量升高。直写成型3D石膏件的抗压强度约为20 MPa, 远高于PBBJ等方法制备的石膏件的抗压强度。     

基于UV油墨的3D地形图呈现

根据地形图的特点及UV油墨快速干燥的特性,提出一种运用3D建模和分层设色的方法,并通过实验,完成了中国台湾省主岛部分3D地形图的打印.选择台湾省主岛部分等高线图,在图形处理软件中,根据其高程,提取多幅等高线矢量图;根据墨层厚度与打印层数的定量关系,得到实际海拔高度与打印层数的对应关系,再根据等高线分层设色原理,设计分层设色对应表,并设定适当的比例尺,确定打印方案;使用喷墨打印机,打印得到具有一定立体感的3D彩色地形图.实验结果表明：根据UV油墨快速干燥的特点,使用UV喷墨打印机,可以打印得到具有立体效果的3D彩色地形图.     

整合纸基微流控检测芯片的食药纸包装

目的探索纸质食品、药品包装与纸基微流控检测芯片的整合方法与规律。方法在传统纸质食品或药品包装的内表面,通过喷蜡打印的方法,整合具有特定生物化学检测作用的纸基微流控芯片,并探索微流体在包装内表面构成的纸基微流控芯片中的运用规律。结果通过喷蜡打印,成功地将纸基微流控芯片整合在了传统纸质食药包装的内表面,经过测试可以完成液体pH检测等基础生物化学检测应用。结论将纸基微流控芯片与食药纸质包装相结合,为食品、药品的实时和现场自我检测提供了新的思路和手段,该方法不仅成本低廉、易于操作,且检测精度高。     

Additive manufacturing of mechanical testing samples based on virgin poly (lactic acid) (PLA) and PLA/wood fibre composites

3D printing in additive manufacturing is considered as one of key technologies to the future high-precision manufacturing in order to benefit diverse industries in building construction, product development, biomedical innovation, etc. The increasing applications of 3D printed components depend primarily on their significant merits of reduced weight, minimum used materials, high precision and shorter production time. Furthermore, it is very crucial that such 3D printed components can maintain the same or even better material performance and product quality as those achieved by conventional manufacturing methods. This study successfully fabricated 3D printed mechanical testing samples of PLA and PLA/wood fibre composites. 3D printing parameters including infill density, layer height and the number of shells were investigated via design of experiments (DoE), among which the number of shells was determined as the most significant factor for maximising tensile strengths of PLA samples. Further, DoE work evaluated the effect of material type (i.e., neat PLA and PLA/wood fibres) and the number of shells on tensile, flexural and impact strengths of material samples. It is suggested that material type is the only predominant factor for maximising all mechanical strengths, which however are consistently lower for PLA/wood fibre composites when compared with those of neat PLA. Increasing the number of shells, on the other hand, has been found to improve almost all strength levels and decrease infill cavities. The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0211-3     

Evolution of 3D Printing Methods and Materials for Electrochemical Energy Storage

Additive manufacturing has revolutionized the building of materials, and 3D-printing has become a useful tool for complex electrode assembly for batteries and supercapacitors. The field initially grew from extrusion-based methods and quickly evolved to photopolymerization printing, while supercapacitor technologies less sensitive to solvents more often involved material jetting processes. The need to develop higher-resolution multimaterial printers is borne out in the performance data of recent 3D printed electrochemical energy storage devices. Underpinning every part of a 3D-printable battery are the printing method and the feed material. These influence material purity, printing fidelity, accuracy, complexity, and the ability to form conductive, ceramic, or solvent-stable materials. The future of 3D-printable batteries and electrochemical energy storage devices is reliant on materials and printing methods that are co-operatively informed by device design. Herein, the material and method requirements in 3D-printable batteries and supercapacitors are addressed and requirements for the future of the field are outlined by linking existing performance limitations to requirements for printable energy-storage materials, casings, and direct printing of electrodes and electrolytes. A guide to materials and printing method choice best suited for alternative-form-factor energy-storage devices to be designed and integrated into the devices they power is thus provided.     

Patterned direct-write and screen-printing of NIR-to-visible upconverting inks for security applications

Two methods of direct-write printing for producing highly resolved features of a polymer impregnated with luminescent upconversion phosphors for security applications are presented. The printed polymer structures range in shape from features to text. The thin polymer features were deposited by direct-write printing of atomized material as well as by screen-printing techniques. These films contain highly luminescent lanthanide-doped, rare-earth nanocrystals, β-NaYF?:3%Er, 17%Yb, which are capped with oleic acid. This capping agent allows the nanocrystals to disperse throughout the films for full detailing of printed features. Upconversion of deposited features was obtained using a 980 nm wavelength laser with emission of upconverted light in the visible region at both 540 and 660 nm. Features were deposited onto high bond paper, Kapton?, and glass to demonstrate possible covert and forensic security printing applications, as they are printed in various features and invisible to 'naked-eye' viewing at low concentrations of nanocrystals.     

Oral disintegrating patient-tailored tablets of warfarin sodium produced by 3D printing

Abstract

Individualized medicine is a new direction in the field of modern pharmacy. In this study, we assessed the feasibility and accuracy of 3D printing techniques for the preparation of individualized doses of mouth-disintegrating tablets of warfarin. Warfarin sodium, D-sucrose, pregelatinized starch, povidone K30, microcrystalline cellulose, and silicon dioxide (at a ratio of 1:42.45:46.15:5.1:4.9:0.4) were mixed and used as the printing powder in the 3D printer; preset parameters were used. The dosage of the tablet was controlled by the number of printing layers. The content, dose uniformity, dose accuracy, hardness, friability, disintegration time, dissolution, and the microstructural and overall appearance were determined to evaluate the printed tablets. For the doses of 3, 2, and 1?mg that were produced in the experiment, the disintegration times were 50.0?±?5.2, 35.7?±?4.3, and 11.0?±?2.2?s, respectively, and the relative errors of the dose were ?2.33, ?1.50, and 0%, respectively. The other indicators were consistent with the preparation requirements of pharmaceutical tablets. It is possible to prepare tablets with excellent properties and controlled drug doses by using 3D printing techniques. This technology will be an important means to achieve individualized medicine.     

Influence of surface chemistry on inkjet printed carbon nanotube films

Carbon nanotube ink chemistry and the proper formulation are crucial for direct-write printing of nanotubes. Moreover, the correct surface chemistry of the self-assembled monolayers that assist the direct deposition of carbon nanotubes onto the substrate is equally important to preserve orientation of the printed carbon nanotubes. We report that the successful formulation of two single walled carbon nanotube (SWNT) inks yields a consistent, homogenous printing pattern possessing the requisite viscosities needed for flow through the microcapillary nozzles of the inkjet printer with fairly modest drying times. The addition of an aqueous sodium silicate allows for a reliable method for forming a uniform carbon nanotube network deposited directly onto unfunctionalized surfaces such as glass or quartz via inkjet deposition. Furthermore, this sodium silicate ingredient helps preserve applied orientation to the printed SWNT solution. Sheet resistivity of this carbon nanotube ink formula printed on quartz decreases as a function of passes and is independent of the substrate. SWNTs were successfully patterned on Au. This amine-based surface chemistry dramatically helps improve the isolation stabilization of the printed SWNTs as seen in the atomic force microscopy (AFM) image. Lastly, using our optimized SWNT ink formula and waveform parameters in the Fuji materials printer, we are able to directly write/print SWNTs into 2D patterns. Dried ink pattern expose and help orient roped carbon nanotubes that are suspended in ordered arrays across the cracks.